<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    .box {
      height: 100px;
      background-color: #f00;
      color: #fff;
      /* 修改div元素的特性:层叠 */
      display: inline;
    }

    span {
      background-color: #0f0;
      display: block;
    }
  </style>
</head>

<body>
  <div class="box">我是div元素</div>
  <span>我是span元素</span>
  <a href="http://www.baidu.com">百度一下</a>
</body>

</html>